Magnetic grappling mechanism for lost well drilling apparatus



` Patented Fel). 6, L1962 of Germany Filed Sept. 29, 1959, Ser. No.843,183 7 Claims. (Cl. 294-655) This invention relates to magneticgrappling mechanism for loose parts of well drilling apparatus lost atthe bottom of the well, and particularly to such mechanism whereinaccidental loss of retrieved parts is avoided.

When drilling wells for the recovery of petroleum, the drillingapparatus sometimes breaks. Many various grappling devices have beendeveloped for the recovery of the loose broken pieces. These devicesmust be adapted to special cases and endeavor to make it possible toremove the blockage to the drilling apparatus in the shortest possibletime.

For the recovery of smaller metal parts of the drilling apparatus, suchas broken cutters or rollers lost from drill bits, a magnetic grapplevcomprising multiple magnets is usually inserted to bring the metalvparts from the bottom of the well to the surface.

At times the magnetic grapple is4 drawn from the well bottom withoutresults. The most frequent cause of this failure is that the grapplemagnets actually attract and pick up the metal parts from the bottom butthese parts are lost again as the string of rods is being raised. Sincethe magnetic contacting surfaces between the metallic parts and themagnets are of rather small area, the magnetic holding forces are weakand only relatively slight resistance is sufficient to pull'or scrapethe recovered parts from the magnets. Rubbing against the uneven wall ofthe well or against the tubing or hard shocks, such as may occur whenstacking the rods, can cause the recovered material to be lost.

In accordance with this invention a mechanism is provided in which themagnet is surrounded by a movable protective pipe or the like which isprovided with grappling means such as springs in order to prevent lossof the retrieved parts.

It is a major object of the invention to provide a novel loose metalpart recovery device comprising magnetic means adapted to be loweredinto a well and having special arrangements for preventing metal objectspicked up thereby from being lost as the device is raised.

A further object of the invention is to provide a novel mechanismprotective arrangement for a magnetic recovery device.

Another object of the invention is to provide a novel magnetic recoverydevice wherein the magnet has associated therewith apparatus that isnormally inoperative as loose metal parts are picked up by the magnetbut which becomes operative as the magnet is raised to prevent loss ofthe retrieved parts.

Another object of the invention is to provide a novel magnetic recoverydevice wherein a magnet is surrounded by a relatively movable protectiveshield that has means for effectively closing blocking its lower end toprevent loss of parts retrieved by the magnet.

Further objects of the invention will appear as the description proceedsin connection with the appended claims and the annexed drawings wherein:

FIGURE l shows apparatus according to a preferred embodiment of theinvention before retrieving the metal parts; and

FIGURE 2 shows the relation of elements after retrieving.

The magnetic grappling mechanism comprises a magnet 1 which is rigidlyconnected to the supporting rod by the connectingl tube 2. The magnetlis surrounded by a protective pipe 3 which is non-magnetic in its lowerportion 3a. The upper edge of pipe 3 carries a safety ring 4 having aninternal annular flange 4. Grappling springs 5, which are capable ofbeing retained in inoperative position, are mounted'at the lower end ofpipe 3. These springs are released by raising the magnet, through anannular release device lwhic'h is at a fixed distance from the magnetsurface.

When the mechanism is assembled the coil spring 7, which surrounds tube2 and is axially disposed between shoulder 8 on the connecting tube-2and shoulder 9 on the protective pipe 3, is placed under compression andheld by means of the shear pin 10 interconnecting tube 2 and pipe 3.When the protective pipe 3 is put down on the bottom ofthe well, the pin10 shears and when the rod is lifted to raiseV tube 2 the protectivepipe 3 is at first maintained on the bottom bythe spring action ofexpanding coil spring 7 while the rising magnet pulls the retrievedmetal parts into the interior of protective Then the release device 6frees the grappling springs 5 as it passes them and these springseifectively close the protective pipe below the magnet.

As the rod is lifted further, the shoulder 8 on the f'connecting tube 2may engage beneath the safety ring flange 4 and pulls the protectivepipe along with it to the surface.

The magnetic body 1 has in its center a channel 11 through which thedrilling mud in the well can circulate. vIt will be noted that permanentmagnet 1 is annular and surrounded by pipe 3. The spring finger retainerdevice 6 is also a ring and, in the position of FIGURE l, it restrainsthe spring leaves 5 from projecting into the interior of the pipe. Eachspring nger 5 is a bent leaf `or blade of spring metal fixed to pipe 3at one end as by a fastener 5 and held stressed in retracted position ininternal slot 5" substantially ush with the pipe bore by ring 6. Y

As tube 2 is raised by the rod or string of rods assembly leading up outof the well magnet 1 rises with respect to pipe 3. Pin 10 is sheared atthis time and the weight on tube 2 is enough to prevent expansion of thespring 7 until tube 2 is sufficiently raised to permit it. In the FIGUREl position spring 7 actually urges pipe 3 toward the well bottom.

After tube 2 raises a certain amount a shoulder 11' on the magnet, orthe tube 2 if desired, engages a flange 6 attached to restraining ring 6and the ring 6 is raised relative to pipe 3 until springs 5 are freed tospring out into the interior of pipe 3 which is otherwise open at itslower end.

Then as the magnet 1 and ring 6 continue to rise together the flange 6'may become interposed between shoulders 11 and 9 to raise to pipe 3 tothe surface along with tube 3. Until shoulder 11' engages ring flange 6spring 7 holds pipe 3 against the well bottom. If flange 6' does notform a connection between the pipe and tube at this point theneventually shoulder 8 engages flange 4 of the safety ring 4 to lift pipe3 along with it to the surface.

Thus it will be seen that as soon as the magnet 1 rises above the levelof ring 6 in FIGURE 1, carrying with it the retrieved metal objects fromthe well bottom into the interior of pipe 3, iinger springs 5automatically extend radially in across the pipe to effectively block itand prevent loss of the retrieved objects even if they should becomedislodged from magnet 1.

The recovered metal parts are brought to the surface p are released fromthe magnet. Thus it is assured that the obstacle to drilling will beremoved by lifting the rod only once.

The invention may be embodied in other speciiic forms without departingfrom the spirit or essential characteristics thereof. The presentembodiment is therefore to be considered in all respects as illustrativeand not restrictive, the scope of the invention being indicated by theappended claims rather than by the foregoing description, and allchanges which come within the meaning and range of equivalency of theclaims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States LettersPatent is:

1. In a grappling mechanism for recovering loose metal objects from thebottom of a Well, a rod-supported member having a magnet on its lowerend, a tubular shield having at least a part surrounding said magnet inspaced relation thereto, a shear element normally holding said magnetand shield in predetermined relative axial position wherein the magnetis disposed near the lower end of the shield in object retrievingposition, said element being broken to permit relative axialdisplacement of the shield and magnet when the shield encounters thebottom of the well, resilient means biasing said shield axially relativeto said magnet, and means actuated after predetermined lifting of themagnet relative to the shield for automatically effectively blockingthelower end of the shield so that retrievedobjects will not be lost evenwhen.

separated from said magnet.

2, In the mechanism defined in claim l, said resilient means being inthe space between said memberand shield and reacting against said memberand acting to normally urge said shield toward the well bottom, andmeans mov-` able with said magnet adapted to engage and lift the shieldas the magnet is raised.

3. In the mechanism defined in claimY l, said` shield being a pipesurrounding themagnet, said means blocking the lower end of the shieldbeing a plurality of spring' fingers normally retained against the boreof the pipe by an axially movable retainer, and coacting means on theretainer and magnet for releasing saidV spring lingers to project intothe interior of saidpipe. after the magnet has been raised apredetermined amount.

4; ln the mechanism defined in claim 3, said retainer being a ringnormally engaging free ends of said spring fingers, and cooperatingaxially engageable projections on the magnet and ring for moving saidring to release said spring fingers.

5. In a magnetic recovery device for retrieving objects from wells, apermanent magnet lowerable into the well, a protective shieldsurrounding said magnet and mounted for relative axial movement, aplurality of internal grappling springs within the lower end of saidshield, means holding said springs in inactive position, and meansoperative after predetermined axial upward displacement of the magnetrelative to said shield for releasing said springs to an active positionextending into the interior of said-shield below the magnet, the lowerend of said shield which mounts said springs being substantiallynonmagnetic.

6. ln the device defined in claim 5, a rod supporting said magnet andsaid magnet being a rigid hollow extension of said rod.

7. In a magnetic recovery device for retrieving objects from the bottomsof wells, a magnet carried by the lower end of a rod, a relativelyaxially displaceable protective References Cited inthe tile of thispatent UNITED STATES PATENTS 2,493,992 VMurphy et al. Ian. l0, 19502,522,294 Noble Sept. 12, 1950 2,539,435. Kirby Jan. 30, 1951 2,613,980Hawkins Oct. 14, 1952 2,657,752 Ballew et al Nov. 3, 1953

